1. Field of the Invention
An embodiment of the present invention relates to a nitride semiconductor light-emitting device and a method for manufacturing the same.
2. Description of the Related Art
An example of a related art nitride semiconductor includes a GaN-based nitride semiconductor. The GaN-based nitride semiconductor is utilized in optical devices of blue/green light-emitting diodes (LEDs), and high speed switching and high power devices such as metal oxide semiconductor field effect transistors (MOSFETs) and high electron mobility transistors (HEMT) also called hetero junction field effect transistors (HFET).
Particularly, a semiconductor light-emitting device having a crystal layer where a Ga position of a GaN-based nitride semiconductor is doped with an element of group II such as Mg and Zn is in the limelight as a device for emitting blue light in the field of light-emitting devices such as LEDs and semiconductor laser diodes of GaN-based nitride semiconductor applications.
The GaN-based nitride semiconductor can be a light-emitting device having a multiple quantum well structure, for example, as illustrated in FIG. 1. The light-emitting device is grown on a substrate 1 primarily formed of sapphire or SiC. Also, a polycrystal thin layer formed of, for example, an AlGaN layer is grown as a buffer layer 2 on the substrate 1 of sapphire or SiC at a low growing temperature, and then a GaN underlayer 3 is sequentially stacked on the buffer layer 2 at high temperature.
An active layer 4 for emitting light is disposed on the GaN underlayer 3. An AlGaN electron barrier layer 5 doped with Mg converted into a p-type layer by thermal annealing, an InGaN layer 6 doped with Mg, and a GaN layer 7 doped with Mg are sequentially stacked on the active layer 4.
Also, an insulating layer 8 is formed on the GaN layer 7 doped with Mg and the GaN underlayer 3. A p-type electrode 9 and an n-type electrode 10 are formed on the GaN layer 7 and the GaN underlayer 3, respectively, so that a light-emitting device is formed.
Referring to FIG. 2, light emitted at the active layer 4 propagates through a light path such as {circle around (4)}, {circle around (2)}, and {circle around (3)}. Here, the light path {circle around (3)} is a path corresponding to total internal reflection where light is totally reflected at a boundary between materials when light is incident from a material having a large refractive index to a material having a small refractive index and the light is incident at an angle equal to or greater than a predetermined angle (i.e., a critical angle).
Therefore, according to the above described related art nitride semiconductor light-emitting device, a portion of light generated at the active layer 4 that propagates through the light path {circle around (3)} is absorbed while it is delivered to a lower side or a lateral side. Accordingly, light-emitting efficiency of the light emitting device including the active layer 4 is considerably reduced.